use { 0, 0, 0, 0 } to fix warning

git-svn-id: http://skia.googlecode.com/svn/trunk@10167 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/MipMapTest.cpp b/tests/MipMapTest.cpp
index 9e1d463..211d1ea 100644
--- a/tests/MipMapTest.cpp
+++ b/tests/MipMapTest.cpp
@@ -31,8 +31,7 @@
         REPORTER_ASSERT(reporter, !mm->extractLevel(SK_Scalar1, NULL));
         REPORTER_ASSERT(reporter, !mm->extractLevel(SK_Scalar1 * 2, NULL));
         
-        SkMipMap::Level prevLevel = { 0 };  // make warnings happy
-        prevLevel.fPixels = NULL;   // sentinel
+        SkMipMap::Level prevLevel = { 0, 0, 0, 0 };
 
         SkScalar scale = SK_Scalar1;
         for (int j = 0; j < 30; ++j) {